The present invention relates in general to hypodermic syringe supporting and operating mechanisms particularly for hypodermic injections of insulin or other fluid doses by the patient himself, and more particularly to a supporting and operating device for hypodermic syringes for removably supporting the syringe, measuring the dose loaded into the syringe, activating the syringe to project the needle into the body tissue to be injected, and automatically aspirating the syringe to withdraw a noticable quantity of blood if a vein has been penetrated.
Heretofore, many spring actuated support devices for hypodermic syringes have been provided to support the plunger and barrel of the syringe and propel them and the needle to the desired injection site in body tissue. Many of these have a foot or contact formation designed to be placed against the external surface of the patient's body into which the needle is to be injected, and a trigger or other release mechanism which permits a cocked spring to propel the needle into the injection site, following which the plunger is mechanically operated to discharge the dose through the needle into the body tissue at the tip of the needle. Usually these are made with expensive parts or of relatively complex construction, increasing difficulty of operation, cost of manufacturing, and possibility of frequent mechanical breakdown. Also, such prior art syringe supporting and injecting devices simply propel the needle and plunger through an advanced stroke when the cocked spring associated therewith is released, having no operating features which provide any indication of whether or not a vein may have been penetrated during injection of the needle into the body. Particularly in the case of insulin injection, it is essential that the tip of the needle not terminate in a vein at the end of the advance stroke, since insulin must never be injected directly into a vein.
Applicant is aware of one prior U.S. Pat. No. 3,702,608, to Tibbs, disclosing a hypodermic syringe supporting and operating device, which also includes operating features whereby aspiration of the syringe occurs during the projection stroke by means of a complex mechanism wherein a syringe plunge holder is supported for reciprocal shifting during the latter part of the injector stroke to achieve aspiration. However, such a construction is complex and expensive to manufacture and a simplification of the supporting device for ease of use and simplicity and economy of manufacture is desired to provide a syringe support and injector device which will have an autoaspirator feature to withdraw a visibly notable amount of blood into the syringe at the completion of the penetration stroke if the end of the needle is located in a vein.
An object of the present invention is the provision of a simplified and less expensive mechanical supporting and operating device for removably receiving and supporting a conventional hypodermic syringe, to support the syringe for spring-driven projection over a predetermined distance to insert the needle to a determined depth into body tissue disposing the tip of the needle a desired distance from a contact foot formation adapted to be placed in abutment with the skin of the patient or user, and wherein the plunger of the syringe is retracted a short distance automatically during the final portion of the projection stroke to aspirate the syringe so that blood will be aspirated into the syringe and be visible if the needle is located in a vein.
Another object of the present invention is the provision of a hypodermic syringe support and operating device as described in the preceding paragraph, wherein a driving spring and releasable latch and trigger mechanism is provided in an inexpensive, simple and reliable mechanical structure.
Another object of the present invention is the provision of a hypodermic syringe support and operating mechanism as described in the two immediately preceding paragraphs, wherein easily movable caliper-type stop arms and spring structure is provided movable between an open position readily receiving a hypodermic syringe plunger between the stop arms and a closed position permitting axial movement of the plunger but engaging and restraining the usual enlarged head or button on the syringe plunger to effect the retraction aspirating stroke.
Another object of the invention is the provision of a hypodermic syringe support and operating device as described in the preceding paragraphs, wherein the contact foot formation adapter to be placed against the skin of the patient or user is shaped to achieve a snap fit with an aligning collar on an insulin bottle or the like, achieving proper alignment of the components to simplify insertion of the needle into the insulin bottle for loading a measured dose of insulin or injection fluid into the syringe.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.